This invention relates generally to a radiation sensitive resist development process and more particularly to a dry development process for resist.
A positive resist system in use today for microlithography applications is composed of an alkali soluble polymer, such as a phenol-formaldehyde Novolak resin and a diazo ketone sensitizer. Such sensitizers and resists are described, for example, in U.S. Pat. Nos. 3,046,118; 3,046,121; 3,106,445; 3,201,239 and 3,666,473; which are hereby incorporated by reference. Exposure to radiation causes the exposed portions of the resist to become soluble in alkaline solutions and normally the resist image is developed in an alkaline aqueous solution. The use of wet developers can result in problems, such as the attack by the alkaline solution on substrate materials such as aluminum, poor profile control, adhesion loss and development bias and tolerance. Recently, dry development techniques have been proposed in which a cold reactive plasma or glow discharge is used in order to selectively remove either the exposed or the unexposed portions of the resist layer. A difficulty in accomplishing dry development is that the plasma removal rates for exposed and unexposed resist are normally not very different.